1. Field of the Invention
The present invention relates to a printing apparatus that carries out continuous printing, in which a large image is printed on a large-sized printing medium.
2. Description of the Related Art
The ink jet printer, which creates dots using a plurality of different color inks ejected from a plurality of nozzles provided on a print head and thereby records an image, has been proposed as an output device of a computer and widely used to print an image processed by the computer in a multi-color, multi-tone manner. This printer enables an image to be printed on a large-sized printing medium, such as a roll of machine glazed paper. Such printing procedure is hereinafter referred to as continuous printing. A large image may be printed on a printing medium of several ten meters, for example, a banner.
There is generally a restriction in quantity of image data processed at once by an application program. In the case of continuous printing, the application program accordingly supplies print data divided in a plurality of pages. In the case of standard printing, a certain margin is present between adjoining pages. The process of continuous printing removes the margin between the adjoining pages and thereby enables an integrated image to be printed while receiving image data divided into a plurality of pages.
The ink jet printer generally uses a print head, on which a large number of nozzles are arranged in a sub-scanning direction, in order to enhance the printing speed. There is a technique called the interlace process, which may be adopted in the ink jet printer with such a print head as one of the recording processes that improve the picture quality.
FIG. 16 shows an example of the interlace process. In the example of FIG. 16, three nozzles are arranged at a nozzle pitch of two dots. Circles in FIG. 16 represent dots created by the respective nozzles. The tens digit in each encircled numeral represents a nozzle number that creates the dot, and the units digit represents the pass of main scan that records the dot. In this example, the 1st pass of the main scan creates dots on the respective raster lin the 2nd nozzle and the 3rd nozzle, whereas the 1st nozzle does not create any dots. After a sub-scan by 3 raster lines, the 2nd pass of the main scan is carried out to form raster lines with all the 1st through the 3rd nozzles. Subsequently the combination of the sub-scan by 3 raster lines with formation of raster lines by each pass of the main scan is repeated to complete an image. As clearly understood from the illustration, no raster line is actually formed with the 1st nozzle on the 1st pass of the main scan, because no raster line that adjoins to the phantom raster line formed with the 1st nozzle on the 1st pass of the main scan can be formed by the 2nd or any subsequent pass of the main scan.
The interlace process forms raster lines intermittently in the sub-scanning direction to record an image. The advantage of the interlace process is that variations of the nozzle pitch and the ink ejection properties can be dispersed on the resulting recorded image. Even when there are some variations in nozzle pitch and ink ejection properties, the interlace process relieves the adverse effects of these variations and improves the picture quality of the resulting recorded image. FIG. 16 shows only an example in which each raster line is formed at a certain nozzle pitch by one pass of the main scan. The image may, however, be recorded according to the interlace process with various amounts of sub-scan, which depend upon the nozzle pitch, the number of nozzles, the number of repeated scans, and other factors.
The interlace process is also applicable to the continuous printing. There are, however, several phantom raster lines, which do not actually contribute to formation of a resulting image, both in an upper end and a lower end of a printing area by the interlace process as clearly shown in FIG. 16. In the case of continuous printing, it is required to print an image without any margins set between each pair of adjoining pages. The presence of such phantom raster lines that do not contribute to formation of an image is accordingly not allowed in the continuous printing. When the continuous printing mode is selected, the conventional technique carries out an upper end process and a lower end process in both the upper end and the lower end of each page, in order to avoid the presence of the phantom raster lines that do not contribute to formation of an image. The upper end process and the lower end process perform the sub-scan by irregular feeding amounts, while recording raster lines as discussed below.
FIG. 17 shows a state of continuous printing by the conventional technique. In the example of FIG. 17, image data divided into N pages are printed in a predetermined area on an integral, continuous printing medium. The upper end process carried out in the upper end of each page and the lower end process carried out in the lower end of each page enable a resulting image to be recorded without any margins between each pair of adjoining pages.
FIG. 18 shows an example of the lower end process. In the example of FIG. 18, the print head has seven nozzles arranged at a nozzle pitch of four dots in the sub-scanning direction. Solid circles represent the positions of the respective nozzles, and encircles numerals represent the nozzle numbers. Broken circles are drawn to clarify the nozzle pitch. Each column, which starts from the left end of the drawing, represents the position of the print head in the sub-scanning direction on each pass of the main scan. Before the lower end process starts, the sub-scan by 7 raster lines is carried out after every pass of the main scan. The lower end process first carries out the sub-scan of 4 raster lines, then repeats the sub-scan of 3 raster lines four times, and subsequently carries out the minute sub-scan of 1 raster line four times. This variation in feeding amount of sub-scan enables an image to be recorded without any drop-out of raster lines up to an end raster line where the 7th nozzle is located on the last pass of the main scan as shown in FIG. 18.
FIG. 19 shows an example of the upper end process. The symbols in FIG. 19 have the same meanings as those of FIG. 18. The upper end process first carries out the minute sub-scan of 1 raster line four times, then repeats the sub-scan of 3 raster lines four times, and subsequently carries out the sub-scan of 4 raster lines. On completion of the upper end process, the standard sub-scan, that is, the sub-scan by 7 raster lines, is carried out after every pass of the main scan. This variation in feeding amount of sub-scan enables an image to be recorded from a 1st raster line where the 1st nozzle is located on the 1st pass of the main scan as shown in FIG. 19.
In the conventional technique of continuous printing, however, there is banding, that is, misalignment of the positions of dot creation, on the boundary between adjoining pages. As described previously, the continuous printing procedure by the conventional technique performs the lower end process to print an image to the lower-most end of each page, and subsequently carries out the sub-scan by a large feeding amount. After the sub-scan by a large feeding amount, the procedure continues printing the image on a next page. By way of example, after a recorded image on the first page is completed by carrying out the lower end process shown in FIG. 18, the sub-scan is carried out by a large feeding amount corresponding to the size of the whole print head. This enables the recording procedure to resume on a 1st raster line in a next page, which is located immediately below the image on the first page, according to the upper end process shown in FIG. 19. In the example of FIGS. 18 and 19, the print head has seven nozzles arranged at the nozzle pitch of four dots, so that the sub-scan by 25 raster lines is carried out on the boundary between adjoining pages.
The greater feeding amount of sub-scan generally results in the lower accuracy of feeding. In the conventional printer that carries out printing on a large-sized printing medium, the lower accuracy of feeding may cause the interval between a lower-most raster line in a certain page and an upper-most raster line in a next page to be significantly different from the interval between another pair of adjoining raster lines. This may cause banding to occur on the boundary between adjoining pages.
In the conventional technique of continuous printing, the banding also occurs in an area where the lower end process is carried out and an area where the upper end process is carried out. In order to complete an image with regard to each page without any margins, it is required to carry out the minute sub-scan of 1 raster line in the lower end process and the upper end process as shown in FIGS. 18 and 19. In the area of the minute sub-scan, a plurality of raster lines adjoining to one another may be formed by the same nozzle. In the example of FIG. 18, the four raster lines located on the lower end are all formed by the 7th nozzle. In the example of FIG. 19, the four raster lines located on the upper end are all formed by the 1st nozzle. In this case, if the 1st nozzle or the 7th nozzle has some displacement of the ink ejecting direction, for example, due to a mechanical error in manufacture, the positions of the four raster lines formed by the 1st nozzle or the 7th nozzle are misaligned collectively. Such misalignment is observed as the banding.
The conventional technique of continuous printing carries out the upper end process, the lower end process, and the minute sub-scan, since the conventional printing apparatus does not allow the print head to sub-scan across a boundary between adjoining pages. The printing process is carried out while the print data are being input successively. Irrespective of the continuous printing mode or the standard printing mode, it can not be determined whether or not a next page is present in the course of the printing process. In the case where the print head is sub-scanned across the boundary between adjoining pages, it may be required to feed the printing medium back in the reverse of the sub-scanning direction at the beginning of the printing process with regard to a next page. In the example of FIG. 16, the printable area is below the raster line where the 2nd nozzle is located at the 1st pass of the main scan. When the print head is allowed unconditionally to sub-scan across the boundary between adjoining pages, on completion of the printing operation in a certain page, the 2nd nozzle is located below the first raster line in a next page where the printing process should start.
The conventional printing apparatus takes into account the above circumstances and carries out the sub-scan without allowing the print head to be located across the boundary between adjoining pages as shown in FIG. 17. In the vicinity of the boundaries in each page, the upper end process and the lower end process are accordingly carried out to implement the sub-scan by certain feeding amounts, which are different from the periodic variation of feeding amount in the other part of the page.
As described above, the banding, however, occurs on the boundary between adjoining pages, the area in which the upper end process is carried out, and the area in which the lower end process is carried out. The presence of the banding undesirably damages the picture quality of the resulting image in the case of continuous printing.
The object of the present invention is thus to prevent banding from occurring in the vicinity of a boundary between adjoining pages in a continuous printing mode, thereby improving the picture quality of a resulting printed image.
At least part of the above and the other related objects is attained by a print controller that generates print data to be supplied to a printer, wherein the printer includes a print head, which has a plurality of dot-forming elements arranged at a preset interval in a sub-scanning direction, and carries out main scan and sub-scan repeatedly, so as to print an image corresponding to the supplied print data on a printing medium. The predetermined image regards a plurality of pages arranged in series in the sub-scanning direction. The print controller includes: an input unit that inputs image data corresponding to the image, page division data that specifies division of each page, and an end-of data code representing an end of the image data; an instruction input unit that inputs an instruction of executing a printing operation in a continuous printing mode, which carries out printing without any margins set between adjoining pages; and a print data generation unit that generates the print data to be supplied to the printer. The print data generation unit has: a feed amount data generation unit that generates feed amount data, which causes the sub-scan to be repeated by a predetermined periodic variation of feeding amount, whether or not an image is completed in each page, when the continuous printing mode is specified; and a raster data generation unit that generates raster data, which specifies a state of dot creation by the print head on each pass of the main scan, based on the image data.
As the print data generated by the print controller of the present invention are output to the printer, the printer carries out both the main scan and the sub-scan based on the input print data and prints an image corresponding to the input print data.
In the conventional printing apparatus, formation of the image is concluded in each page as described previously. The conventional printing apparatus carries out the printing process while successively receiving the supply of image data. In the case where a specific signal is input in the end of the image data to specify a new page, a shift to the new page is implemented in response to the specific signal. It can not be determined whether or not a next page is present, based on the specific signal for specifying a new page. The conventional technique accordingly concludes formation of the image in each page, in order to enable the printing process to be completed in each page, irrespective of the presence or non-presence of a next page. As described previously, the upper end process and the lower end process are carried out in the vicinity of the boundaries of each page to implement the sub-scan by certain feeding amounts, which are different from the periodic variation of feeding amount in the other part of the page. This arrangement prevents the print head from being located across the boundary between adjoining pages, thereby avoiding the requirement that feeds the printing medium back in the reverse of the sub-scanning direction at the start of the printing operation of each page.
When the continuous printing is specified, the technique of the present invention, on the other hand, carries out the sub-scan by the predetermined periodic variation of feeding amount, whether or not formation of the image is concluded in each page. The sub-scan by such a periodic variation of feeding amount may cause the print head to be located across the boundary between adjoining pages. In such a case, the technique of the present invention supplies image data of each page according to the position of the dot-forming element and carries out the printing operation. The image data with regard to a current page is supplied to the dot-forming element that is located in the current page across the boundary between the adjoining pages, whereas the image data with regard to a next page is supplied to the dot-forming element that is located in the next page. In the case where no next page is present, the image data are supplied only to the dot-forming element that is located in the current page.
When the continuous printing is specified, the technique of the present invention prints an image with the predetermined periodic variation of feeding amount maintained, whether or not formation of the image is concluded in each page. This arrangement does not require the sub-scan by a significantly large amount on the boundary between adjoining pages. This arrangement does not conclude the printing process in each page, thereby not requiring the lower end process or the upper end process including the minute sub-scan. The technique of the present invention thus effectively prevents the banding from occurring on the boundary between adjoining pages and improves the picture quality of the resulting printed image. The arrangement of maintaining the predetermined periodic variation of feeding amount significantly facilitates the control of the printing procedure. The principle of the present invention is especially effective when an integrated, continuous image that is continuous across the boundary between pages is printed.
The technique of the present invention is effectively applicable to print individual images, which are divided by pages, continuously without any margins. An example of the applicable cases continuously prints a plurality of photographs on a long printing medium without any margins. This arrangement facilitates the control of the printing procedure. This arrangement does not require the upper end process or the lower end process, which generally lowers the efficiency of printing, thereby improving the printing rate.
The specification of the continuous printing is generally given to an extremely long printing medium, such as a roll of machine glazed paper. In the case where the size of the printing medium does not allow sufficient margins relative to an image printing area, the sub-scan to the vicinity of the terminal end of the printing medium may cause the significantly lower accuracy of feeding in some sub-scan mechanisms. In the case of continuous printing, on the other hand, the size of the printing medium generally allows sufficient margins relative to the image printing area. The present invention takes account of this characteristic of continuous printing and breaks the obsession that should not allow the print head to be located out of a predetermined size of the printing medium at least in the last page. This enables an improvement in picture quality, while ensuring the simplified printing procedure in the continuous printing mode. The simplified printing procedure naturally enhances the printing speed.
The predetermined periodic variation of feeding amount may be a fixed feeding amount, or may alternatively include two or more different feeding amounts which are periodically repeated. The periodic variation of feeding amount depends upon the number of the dot-forming elements and their pitch. In the arrangement of the present invention, the predetermined periodic variation of feeding amount may not be maintained strictly in all the area. A different feeding amount may, however, be adopted in a narrow area specified in advance.
In accordance with one preferable embodiment of the print controller, the feed amount data generation unit generates the feed amount data that represents a specific feeding amount of the sub-scan, which is adopted prior to the predetermined periodic variation of feeding amount in a first page among the plurality of pages, so as to enable the main scan without causing any dropout of a raster line in a certain area that is out of a main area, in which the predetermined periodic variation of feeding amount is adopted. The specific feeding amount is smaller than a mean feeding amount, which is calculated from the predetermined periodic variation of feeding amount.
This arrangement enables the upper end process to be carried out on the upper end of the first page like the conventional technique, thereby expanding the printable area on the upper end of the first page. The certain area in the above embodiment corresponds to an expanded area. The actual amount of feeding may be set arbitrarily according to the range of the certain area, the pitch of the dot-forming elements, and the number of passes of the main scan required to form each raster line.
In accordance with one preferable application of the present invention, the raster data generation unit, in the case of an input of the page division data, waits for an input of image data with regard to a next page following the page division data and then generates the raster data. In the case of an input of the end-of-data code, on the other hand, the raster data generation unit generates the raster data without waiting for further input of image data.
This arrangement enables the printing operation of the image to be performed appropriately, depending upon whether or not a next page is present after the boundary, when the print head is located across the boundary. The page division data and the end-of-data code may be any data structure, as long as they are explicitly distinguishable from general image data.
In accordance with another preferable application of the present invention, the print data generation unit sets a sufficiently large value, which is greater than the plurality of pages, to a size of the printing medium and subsequently generates the print data, when the continuous printing mode is specified.
This arrangement enables image data divided into a plurality of pages to be processed virtually as data of a single page. Setting a sufficiently large value to the size of the printing medium ensures the continuous printing according to the same procedure as that of the standard printing.
The printing apparatus of the present invention may be used exclusively for the continuous printing, or may alternatively be used for both the continuous printing and the standard printing. In accordance with one preferable embodiment of the present invention, the instruction input unit selectively inputs the instruction of executing the printing operation in the continuous printing mode and an instruction of executing a printing operation in a standard printing mode, which carries out printing with a margin set between adjoining pages. The feed amount data generation unit generates the feed amount data that represents a specific feeding amount of the sub-scan set in advance to enable the main scan to be performed without causing any dropout of a raster line in each page, in response to the instruction of executing the printing operation in the standard printing mode. The raster data generation unit generates the raster data with regard to each page, based on the image data input before the page division data.
This arrangement enables the standard printing with margins set for each page and the continuous printing to be carried out selectively, thereby improving the usability of the printing apparatus.
The present invention is also directed to a variety of printing apparatuses, each including the print controller having any one of the above configurations and the printer.
The printing apparatus may further include a reverse feeding unit that feeds back the printing medium, which has been fed excessively by a printing operation in a last page among the plurality of pages, in reverse of a printing direction to a certain position suitable for starting a next cycle of the printing operation.
As described previously, the technique of the present invention does not carry out the lower end process even in the last page of the image and performs the printing process with the predetermined periodic variation of feeding amount maintained. This may cause a specific area on the printing medium, which follows the last page, to be wasted. The reverse feeding unit feeds the excessively fed printing medium back and thereby enables the specific area, which is possibly wasted, to be used for a next cycle of printing. For example, the reverse feeding unit specifies the size of the specific area, which is possibly wasted, by the excess feed of sub-scan and feeds the printing medium back to a certain position suitable for a start of the next cycle of printing. In another example, the reverse feeding unit feeds the printing medium back to a state prior to the supply to the printing apparatus and supplies the printing medium again. The reverse feeding process may be performed on completion of printing an image or prior to a start of the next cycle of printing.
The present invention is further directed to a method corresponding to the print controller discussed above, a method corresponding to the printing apparatus discussed above, as well as a recording medium, on which a program for generating data to be supplied to the printer is recorded, the program itself, and a variety of other applications.
Typical examples of the recording medium include flexible disks, CD-ROMs, magneto-optic discs, IC cards, ROM cartridges, punched cards, prints with barcodes or other codes printed thereon, internal storage devices (memories like RAM and ROM) and external storage devices of the computer, and a variety of other computer readable media.
These and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiment with the accompanying drawings.